The various laws related with the fire safety are:
- National Building Code.
- B.I.S. Codes.
- Fire Bylaws.
State Governments have enacted bylaws like Delhi fire bylaws which are to be adhered to when constructing a high rise building. These bylaws have a statutory force. Designer must obtain and study the fire bylaws applicable to the particular area while planning. For the purpose of these regulations all buildings with height more than 15m are considered high rise buildings.
Also in the department a fire protection manual has been prepared by Electrical Wing of DOT in consultation with Switching and BW group of directorate. This manual is for technical buildings of the DOT.
These should be referred while designing a fire protection system. These has been considered in brief in the following design of building and services for fire. The manuals and bylaws however should always be referred for getting the information in detail.
Following services should be considered in this context:
- Building planning and design
- Electrical Installation
- Transformer Substation
- Lift and Fire Lift
- Standby Electric Supply
- Telecom Equipment
I. BUILDING PLANNING AND DESIGN:
Type of Construction:
- All MAX-I, MAX-II, Telecom buildings having TAX and trunk exchanges and administrative buildings shall confirm to the requirements of Type-I construction as per NBC.
- Max-III and other small local exchanges may be housed in type 2 & 3 building depending on the fire hazard in the area in which they are situated.
Material of Construction:
- External walls and enclosing walls of staircases shall be only of brick, RCC or hollow CC blocks. Thickness of these walls shall not be less than 200 mm. However, if panel area exceeds 40 m² the minimum thickness of these walls shall not be less than 300 mm.
- Internal Partitions: The panel of partition shall be of fire retardant material confirming to class-I (Surface of very low spread of flame as per IS 1642. Only metallic framework shall be used in partitions. Wherever particle boards/gypsum boards are used in the internal partitions in technical buildings, these shall be painted with fire retardant paint of approved quality. The thickness of glass in glazed partition should not be less than 5.5 mm.
- Executive cabins, cashier cabins and partitions in Administrative Buildings should be in fire resistant material such as regular bricks walls etc. Avoid temporary partitions and consequent fire hazards.
- Windows and Glazings: In all telecom buildings, windows and fixed glazings with metallic frames shall be used. Glasses shall be fixed to the sashes by metal beading. The external glazing shall have wired glass. In the switch-room, OMC and exploitation rooms, bill centers and software centers etc external will have double glass and outer glazing shall be wired glass 5.5 mm thick.
- Doors and Shutters: Fire check shutters shall generally confirm to IS 3614. The doors opening in the staircase, lift lobbies shall have minimum of one hour fire resistance. The minimum thickness of the lobby door shall be 50 mm. Only metallic doors shall be used in electrical sub-stations.
- False Ceiling: It is preferable to avoid provision of false ceiling. However if false ceiling could not be avoided, metallic frames shall be used. The panel of partition shall be of fire retardant material confirming to class-I (flame spread category). Use of polythene sheet covers to wrap the mineral or rock wool pads placed over false ceiling shall be avoided and may be wrapped in Aluminum foils.
- Floor Coverings: Jute matting shall not be permitted for floor covering telephone exchanges. It shall be pre-laminated fire retardant category board. The laminates of false floor/floor covering shall confirm to class-I fire retardant quality.
- Wall Paneling: It is preferable to avoid provision of wall paneling. However, if wall panelings are considered necessary for acoustic treatment, Gypsum boards or fire retardant material confirming to class-I flame spread category shall be used. The frame work of wall paneling shall be metallic.
- Limitation in the use of synthetic products and materials: In the interior fitting of all technical buildings, use of synthetic materials and products such as plastic materials, synthetic fibers, textiles etc whose composition contains nitrogen or chlorine, likely to be discharged in the form of hydrocynamic or hydrochloric acid fumes shall be avoided as far as possible. Internal fittings deemed to be include coverings of wall, partitions, ceilings, decorations, tapestry, curtains, conduits or pipe work non-incorporated or non-embedded fixed furniture etc.
- All furniture in the equipment room shall be of steel. Use of plastic or wooden furniture shall not be permitted in technical buildings.
- In general, all buildings shall be strictly adhered according to the local building bylaws relating to maximum height, FAR (Floor Area Ratio), open space etc. Most populated areas shall be located in lower floor to facilitate evacuation and dependency of lift at the time of hazard.
- Open Spaces (High Rise Buildings): Compulsory open space around the buildings (4.5 m open space around the building for free movement of fire fighting vehicle) shall be provided and no parking should be done in this area. The turning radius should no be less than 9 m. Entry gate width should not be less than 5 m (clear). (As per Delhi Fire Prevention & Fire Safety Act 1986, 6 m access around the building is required.)
- Protection of Openings: Openings in the walls and floors which are necessary to be provided to allow cables/electrical wiring/telecom cables/plumbings and fixtures shall be sealed by a filler material of vermiculite concrete or compressed asbestos fiber mixed with cement or any other filler material having Fire Resistance (F.R.) not less than 2 hours. These openings in the floor/walls shall be protected by vertical/horizontal enclosures of at least 300 mm extending beyond these openings.
- Ventilation of Basements: The basement shall be ventilated by suitable vents of cross-sectional area not less than 2.5 % of the floor area spread evenly round the perimeter of the basement.
- Canteens, fuel storage shall not be permitted in the basement. These should be preferably in a separate block. Use of corridors for keeping lockers should be avoided and separate rooms shall be provided to keep the corridors free of obstruction to the movements.
Service ducts shall be enclosed by walls and doors of 2 hours F.R. If the plan of duct exceeds 1 sq.m, slab shall be provided at each floor to seal the remaining areas after providing the pipes, conduits, AC ducts etc.
- Separation of Switch room from other areas: switch-room / OFC room should be separate from other areas rooms by wall having a minimum 2 hours F.R. (200 mm brick wall plastered on both sides). If it is not structurally feasible to provide brick wall, partition of light cellular concrete panel shall be provided.
- Every building shall be provided with exits sufficient to permit safe escape of the occupants in the case of fire or other emergency. All exits and routes leading to the exits shall be free from obstructions. Exits shall be clearly visible and route of the exits shall be clearly marked with red arrows painted on luminous transparencies. All exits shall provide continuous means of access to the exterior of a building or to an exterior open space leading to a street. Exits shall be so arranged that they may be reached without passing through another occupied unit.
- Fire resisting doors with at least one hour fire resistance shall be provided at the exit from each equipment room. The doors at entries to staircase/lift lobbies shall have minimum one hour fire resistance.
- Travel Distance: Exits shall be so located that the travel distance to an exit shall not exceed 22.5 m.
Width: The unit of width of exits shall be 50 cm. The width of 25 cm. shall be counted as half unit. Maximum number of occupants per unit exit width shall be as under:
- Stairways: 50
- Ramps: 60
- Doors: 75
- For determining exit requirements, the number of persons within any floor area shall be based on actual number subject to a minimum of 10 m² per person. The minimum width of stairs shall be 1.5 m. The width of exit doors shall be minimum 1 m. (Note: For detailed exit width requirement refer to IS l644 - Code of Practice of Fire Safety of Buildings: Personal Hazards).
- Number of Staircases: All buildings more than 15 m in height and all MAX I and TAX buildings, shall have a minimum of two staircases. Any building with more than 500 Sq.m. area on each floor shall also have minimum of two staircases.
- The staircases shall be of enclosed type and at least one of them shall be ventilated to the atmosphere at each landing and with a vent at the top. For buildings more than 24 m in height or more than 6 storey, one of the stairs shall be a fire tower enclosed with wall of 4 hours fire resistance. The internal walls of staircase shall be of brick or reinforced concrete with a minimum of 2 hours fire resistance.
- In multi-storey buildings, if the staircase cannot be ventilated because of its location or other reasons it shall be mechanically pressurized with a positive pressure of 5 mm water gauge. The mechanism for pressurization shall operate automatically with the fire alarm.
- Treads and Risers: The minimum with of treads without nosing shall be 30 cm. and the maximum height of the risers shall be 19 cm. Not more than 15 Risers shall be provided in one flight. Spiral type arrangement should be avoided.
- Handrails: The minimum height of hand rails shall be 100 cm. and gap between two verticals shall not exceeds 30 cm. The hand rails shall be of a material conforming to Class-1 (Surface of very low flame spread).
- Exit from Basement: The maximum travel distance to the staircase of basement shall not exceed 18.5 m, otherwise additional staircase shall be provided. However there shall be at least two exits from basement. The staircase of basement shall be enclosed type having a fire resistance of not less than 2 hours and shall be situated at the periphery in such a way that exterior of the buildings or an open space is reached without passing through an occupied area on the ground floor.
Lift and Lift Lobbies:
- Walls of lift lobbies shall have a fire rating of two hours.
- Lift machine room shall be located in the top of the lift shaft and shall be separated from the lift shaft, by the floor of the room.
- Number of lifts in one lift bank shall not exceed four. Individual shafts in a bank shall be separated by a wall of two hours fire rating.
- The lift car shall have a minimum of one hour fire rating. Collapsible gates shall not be permitted for lifts and shall have solid doors.
- If the lift lobby and lift shaft is in the core of the building, a positive pressure of 2.5 mm of water gauge shall be maintained in the lobby and 5 mm. in the lift shaft. The pressurization mechanism shall start automatically on the fire alarm. It shall be possible to operate this manually also.
- Telephone or other communication facilities shall be provided in the lift cars.
- To enable the fire service personnel to reach the upper floor with minimum delay, one or more lifts shall be designated as 'FIRE LIFTS' so as to be available for exclusive use of the Firemen in an emergency. Such lifts shall have automatic closing doors and a minimum capacity of 8 persons. These Fire Lifts shall have alternative source of power supply also. The words 'FIRE LIFT' shall be conspicuously displayed on the landing doors at each floor level. A toggle switch shall be provided at the ground floor lobby for 'FIRE LIFTS'. This switch shall be provided at 2 m above the floor level and shall be provided with a glass cover. On operation of this switch by fire personnel, the lift car will come to the ground floor straight and there after its operation shall be controlled only from inside the lift car.
- Lift shall not normally communicate with the basement. However, one of the lifts may be permitted to reach the basement levels provided the lift lobby at each basement level is pressurized and separated from the rest of the basement area, by smoke actuated fire resisting door of two hours fire resistance.
Fire Control Room:
- For all High Rise Buildings there shall be a control room of 4 m × 4 m (minimum) at the ground floor entrance lobby of the building with communication system (suitable public address system) at all floors and facilities for receiving message from different floors. Details of all floor plans along with details of fire fighting equipment installation in the building shall be maintained in the fire control room. This room shall also have facilities to detect the fire on any floor through Indicator boards connecting the fire detecting and alarm system on all floor. The staff in-charge of fire control room shall be responsible for the maintenance of various emergency services, fire fighting equipment and installations.
II. ELECTRICAL INSTALLATION:
- The electrical installation shall generally confirm to IE Rules 1956, IS codes and specifications of the department.
- For DBs metallic shutters and frames shall be used.
- Switch boards shall be erected in an easily accessible position and shall have a clear space not less than 1 m in the front side. The space behind the switchboard shall be either less than 200 mm or more than 750 mm clear. If the space behind the switch-room exceeds 750 mm in width, there shall be a passage way from either end of the switchboard with a clear height of 1800 mm.
- No articles shall be stored at the back of the switch boards.
- The inspection panel doors and other openings in shaft shall be provided with airtight fire doors having fire resistance of not less than 2 h.
- All switches and circuit breakers shall be operated from the front of the switch boards.
- All screws, bolts and nuts which secure current carrying parts to the board shall be of brass, copper or equivalent rust proof material.
- Wood work shall not be used in the construction of the enclosure of the switchboard except for shutters lined on both sides with fire resisting material e.g. G.I. sheet.
- The neutral of each main or branch main circuit shall be provided with a suitable removable link placed in an easily accessible position for the purpose of testing. The neutrals shall not be bunched in inconvenient and inaccessible position at the back.
- All equipment of power distribution boards shall be of iron clad or steel construction throughout and dust tight.
- End of conduits shall be bushed and glands shall be provided for armoured cables. All unused cable holes shall be effectively closed.
- Correct rating of fuses shall be used.
- All surface wiring shall be in metallic conduits/enclosures. Joint boxes, inspection bends, drawing-in-boxes shall be covered at all times with metal covers.
- T-joints in power wiring shall not be permitted. Joints if any in wires and cables shall be crimped joints.
- Temporary wiring and extension circuits should not be ordinarily permitted. Wherever extension circuits are needed those shall be installed only after prior approval of the maintenance personnel.
- All circuits shall be clearly and indelibly labelled for identification.
- Medium and low voltage wiring running in shaft, and within false ceiling shall run in metal conduit. Any 230 V wiring for lighting or other service, above false ceiling shall have 660 V grade insulation. The false ceiling including all fixtures used for its suspension shall be of noncombustible material.
- Telephone or other wiring not pertaining to lighting and power system shall be spread at least 300mm from it throughout installation.
- Separate circuits for water pumps, lifts, staircases and corridor lighting and blowers for pressurizing system shall be provided directly from the emergency LT panel (Supply from mains as well as standby source with changeover arrangement). Switches controlling essential services shall be clearly labelled.
- Emergency lights shall be provided in lobbies, corridors and technical rooms.
Staircase and Corridor Lights:
- The staircase and corridor lighting shall be on separate circuits and shall be independently connected so that it could be operated by one switch installation on the ground floor easily accessible to fire fighting staff at any time irrespective of the position of the individual control of the light points, if any. It should be of miniature circuit breaker type of switch so as to avoid replacement of fuse in case of crisis.
- Staircase and corridor lighting shall also be connected to alternative supply for building exceeding 24 m in height. For assembly, institutional buildings of height less than 24 m, the alternative source of supply may be provided by battery continuously trickle charged from the electric mains.
- Suitable arrangement shall be made by installing double throw switches to ensure that the lighting installed in the staircase and the corridor does not get connected to two source of supply simultaneously. Double throw switch shall be installed in the service room for terminating the stand-by supply.
- Emergency light shall be provided in staircases/corridors.
- The electric distribution cables/wiring shall be laid in a separate duct. The duct shall be sealed at every alternative floor with non-combustible materials having the same fire resistance as that of the duct.
- Wiring to and fro from the switch-gear shall be of armoured cables and with conduit/metallic covering. Flexible tubing shall not be allowed excepting for connections to motors and starters, but the length shall be restricted to 1200 mm.
- An independent and well ventilated service from floor with direct access from outside or from the corridor for the purpose of termination of electric supply from the licensees' service and alternative supply cables. The doors provided for the service room shall have fire resistance of not less than 2 h.
- If the licensees agree to provide meters on upper floors, the licensees' cables shall be segregated from consumers cable by providing a partition in the duct. Meter rooms on upper floors shall not open into staircase enclosures and shall be ventilated directly to open air outside.
- Water mains, telephone lines, intercom lines, gas pipes or any other service line shall not land, in the duct for electric cables.
- All earthing leads and earth connections shall be tested for electrical resistance to ensure efficient earthing before electric supply lines or apparatus is energized. In addition earth resistance shall be tested on a day during dry season not less than once a year and record of resistance measured shall be kept in a log book.
III. TRANSFORMER SUBSTATIONS:
- The sub-station shall preferably be located in a separate building. The supply company’s HT switch-gear and metering equipment shall be placed in a separate enclosure approachable by supply company at all times.
- When housed at ground floor level, it/they shall be cut off from the other portion of premises by fire resisting walls of 4 h fire resistance (230 mm thick walls).
- Sub station or a switch-station with apparatus having more than 2000 liters of oil shall not ordinarily be located in the basement, where proper oil drainage arrangements cannot be provided. If transformers are housed in the building below the ground level, they shall necessarily be in the first basement in a separate fire resisting room of 4 h rating. The room shall necessarily be at the periphery of the basement. The entrance to the room shall be provided with a fire resisting door of 2 h fire rating. A curb (sill) of a suitable height shall be provided at the entrance in order to prevent the flow of oil from ruptured transformer into the other parts of the basement. Direct access to the transformer room shall be provided, preferably from outside. The switch-gears shall be housed in a room separated from the transformer bays by a fire resisting wall with fire resistance of not less than 4 h.
- The transformer, if housed in basement, shall be protected by an automatic high velocity spray system.
- In case the transformer are housed in the basement, totally segregated from other areas of the basement by 4 h fire resisting wall/walls with an access directly from outside, they may be protected by carbon dioxide or BCF (Brochlorodifluormethane) or BTM (Mromotrifluoromethane) fixed installation system.
- Oil filled transformer shall not be housed on any floor above the ground floor.
- Soak pit of approved design shall be provided where the aggregate oil capacity of the apparatus does not exceed 2000 liters. Where the oil capacity exceeds 2000 liters, a tank of RCC construction of capacity capable of accommodating the entire oil of the transformers shall be provided at a lower level to collect the oil from the catch pit in case of emergency. The pipe connecting the catch pit to the tank shall be of non-combustible construction of minimum 150mm diameter and shall be provided with a flame arrestor. The distance of soak pit shall not be more than 2.5 m away from the substation.
- Cable trenches shall be filled with pebbles or similar non-inflammable material and covered with non-inflammable slabs.
- All control gears shall be protected against rodents, reptiles and insects.
- Sub-station shall be suitably ventilated. All cable ducts and openings shall be sealed off and ventilator shall be made inaccessible to birds by wire gauge screens.
- Sub-station building shall be used for housing only the intended equipment and not for storage or repair works.
- Suitable extinguishers shall be provided in substation room.
- The materials used for insulting the duct system (inside or outside) shall be of noncombustible materials. Glass wool shall not be wrapped or secured by any material of combustible nature. Cladding provided shall be with GI or aluminum or any such non-combustible material.
- The ducting shall be constructed of substantial gauge metal in accordance with good practice.
- Wherever the ducts pass through fire walls or floor, the opening around the ducts shall be sealed with fire resisting materials, such as asbestos rope, vermiculite concrete, etc.
- Air duct servicing main floor area, corridors etc, shall not pass through the staircase enclosure.
- As far as possible, metallic ducts shall be used even for the return air instead of space above the false ceiling.
- Inspection panels shall be provided in the main trunking to facilitate the cleaning of ducts of accumulated dust and to obtain access for maintenance of fire dampers.
- No combustible material shall be fixed nearer than 15 cm to duct unless such duct is properly enclosed and protected with non-combustible material (glass wool or spun-glass with neoprene facing enclosed and wrapped with aluminum sheet of at least 3.2 mm thick and which would not readily conduct heat.
- As far as possible, ducts shall not cross power bus bars in equipment rooms. However, if the crossing is unavoidable, suitable protection shall be provided.
Air Handling Unit:
- The air-handling units shall be separate for each floor and air ducts for every floor shall be separate and in no way interconnected with the ducting of any other floor.
If the air-handling units serves more than one floor, the recommendations given above shall be complied with in addition to the condition given below:
- Proper arrangements by way of automatic fire dampers working on fusible link for isolating all ducting at every floor from the main riser shall be made.
- When the automatic fire alarm operates, the respective air-handling units of the air-conditioning system shall automatically be switched off.
- The air filters of the air-handling units shall be of non-combustible material.
- The air-handling unit room shall not be used for storage of any combustible materials.
- The air handling unit/plant room located adjacent to the equipment room shall be separated by a partition of minimum 2 hours F.R.
- The vertical shaft for treated fresh air shall be of masonry construction.
- Escape routes like staircases, common corridors, lift lobbies etc, shall not be used as return air passage. However, if unavoidable, the return air boxing shall be fabricated from fire proof material.
- Where plenum is used for return air passage ceiling and its fixture shall be of non-combustible material.
- Area more than 750 m² on individual floor shall be segregated by a fire wall and automatic fire dampers for isolation shall be provided.
- All ducts emerging from weather maker unit shall be provided with fire dampers.
These shall be located in conditioned air ducts and return air ducts/passages at the following points:
- At the fire separation wall.
- Where the ducts/passage enter the central vertical shaft.
- Where the ducts pass through floors.
- At the inlet of supply air duct and the return air duct of each compartment on every floor.
- The dampers shall operate automatically and shall simultaneously switch off the air-handling fans. Manual operation facilities shall also be provided.
- Automatic fire dampers shall be so arranged so as to close by gravity in the direction of air movement and to remain tightly closed upon operation of a fusible link.
Automatic shut-off on fire alarm:
- In all plants there shall be a provision for automatic switch off of the respective air handling units/package plant with the operation of the fire alarm.
As soon as the blower is stopped, the package plant / AHU / heater element should get switched off automatically.
- In addition to the above, thermostat control should be provided to switch off the heaters whenever the air flow stops and the temperature rises beyond a predetermined level.
V. LIFTS & FIRE LIFT:
- Walls of lift enclosures shall have fire rating of 2 h lift shafts shall have a vent at the top of area not less than 0.2 m².
- Lift motor room shall be located preferably on top of the shaft and separated from the shaft by the floor of the room.
- Landing doors in lift enclosures shall have a fire resistance of not less half an hour.
- The number of lifts in one lift bank shall not exceed four. Individual shafts in a bank shall be separated by a wall of 2 h fire rating.
- Lift car door shall have a fire resistance rating of 1 h.
- For buildings above 15 m in height, collapsible gates shall be permitted for lifts and shall have solid doors with fire resistance of at least l h.
- If the lift shaft and lobby is in the core of the building, a positive pressure between 25 and 30 Pa shall be maintained in the lobby and a positive pressure of 50 Pa shall be maintained in the lift shaft. The mechanism for pressurization shall act automatically with the fire alarm; it shall be possible to operate this mechanically also.
- Exit from the lift lobby, if located in the core of the building shall be through a self-closing smoke stop door of half an hour fire resistance.
- Lifts shall not normally communicate with basement; if however, lifts are in communication, the lift lobby of the basement shall be pressured as in (g) with self-closing door as in (h).
- Grounding switch(es) at ground floor level, shall be provided to enable the fire service to ground the lifts.
- Telephone or other communication facilities may be provided in lifts cars for building of 30 m in height and above. Communication system for lifts shall be connected to fire control room for the building.
- Suitable arrangements such as providing slope in the floor of lift lobby, shall be made to prevent water used during fire fighting etc at any landing from entering the lift shaft.
- A sign shall be posted and maintained on every floor at or near the lift indicating that in case of fire, occupants shall use the stairs unless instructed otherwise. The sign shall also contain a plan for each floor showing the location of the stairways.
- To enable fire service personnel to reach the upper floors with the minimum delay, one or more of the lifts shall be so designed so as to be available for the exclusive use of the fire-man in an emergency and be directly accessible to every dwelling / lettable floor space on each floor.
- The lift shall have a floor area of not less than 1.4 m². It shall have loading capacity of not less than 545 kg (8 persons) with automatic closing doors.
- The electric supply shall be on a separate service from electric supply mains in a building and the cables run in a route safe from fire. Lights and fans in the elevators having wooden paneling or sheet steel construction shall be operated on 24 volts supply.
- In case of failure of normal electric supply, it shall automatically trip over to alternate supply. For apartments/houses, this changeover of supply could be done through manually operated change over switch. Alternatively, the lift should be so wired that in case of power failure, it comes to standstill with door open.
- The operation of a fire lift is by a simple toggle or two button switch situated in a glass fronted box adjacent to the lift at the entrance level. When the switch is on, landing call points will became inoperative and the lift will be on car control only or on a priority control device. When the switch is off, the lift will return to normal working. The lift can be used by the occupants in normal times.
- The wards "FIRE LIFT" shall be conspicuously displayed in fluorescent paint an the lift landing doors at each floor level.
- The speed of the fire lift shall be such that it can reach the top floor from ground level within one minute.
VI. STAND BY POWER SUPPLY:
A stand-by electric generator shall be installed to supply power to staircase and corridor lighting circuits, fire lifts, the stand-by fire pump, pressurization fans and blowers, smoke extraction and damper system in case of failure of normal electric supply. The generator shall be capable of taking starting current of all the machines and circuits stated above simultaneously. If the stand-by pump is driven by diesel engine, the generator supply need not be connected to the stand by pump. Where parallel HV / MV supply from a separate sub station is provided with appropriate of generator may be waived in consultation with the authority.
ENGINE ALTERNATOR ROOM: Only incandescent electric lighting shall be used for E/A room. Naked light shall not be used. Wall plugs shall not be used in the E/A room. E/A room shall be well ventilated with exhaust fans. Individual capacity of tank shall not be more than 1000 litres.
VII. TELECOM EQUIPMENT:
- Experience shows that most of the fires in Telephone Exchanges originate from the electrical faults in the power wiring or in the equipment itself. It is therefore essential that power wiring is done as per the good engineering practice. Power distribution in the switch-rooms shall be done according to the engineering instructions issued for the type of Exchange such as E-10B / C-Dot etc. as the case may be.
- Separation of AC/DC Distribution: AC input leads and DC input leads shall not travel in the same rack / run-way side by side.
- Terminations of Leads: The leads shall be fixed tightly to the terminals and shall preferably have crimped connections. Nuts and bolts used for connecting the terminals or bus bars or fish-plates should be of proper size and well tightened.
- Earthing: Power plant as well as other equipment shall be properly earthed. The frame earth and battery earth shall be separate and shall maintain a resistance not exceeding 0.5 ohms for all electronic exchanges. Bare Stranded conductor without any joint shall be used as earth lead right from the spike or plate earth up to the earth terminal in the power room. In case of multi-exchange buildings, each exchange shall have separate earth.
- Communication Cables: Communication cables shall be laid at a safe distance from the power cables.
- Extension Work: Power distribution work for extensions shall be done by a specialized group under high level supervision to ensure that prescribed practices are strictly followed. Utmost care shall be taken to ensure that no bare conductor touches the live bus bars.
- Fire Fighting Instructions Display: Clear cut instructions regarding operations to be carried out in case of fire shall be displayed prominently all equipment rooms.
Protection / Isolation:
- Adequate protection / isolation facility should be available in the AC/DC distribution system by provision of fuses/circuit breakers. The Circuit breakers shall have manual tripping facility.
- Suitable arrangement to shut off the rectifier whenever the input voltage goes beyond the specified limit shall be provided in the power plant with alarm indication.
- The distribution fuses/circuit breakers shall be rated for maximum load condition and should be easily accessible.
- Bare fuse wires or strands of copper wire should not be used to replace blown alarm-type fuses. Fuses of correct type and size must only be used for replacement. All mains supply fuses should be inside their covers or cartridges and not exposed. It is necessary that all alarm type fuses should have the correct colour beads fitted on them. Only fuse wire of correct rating should be used for their repairs.
- All power leads, especially those carrying heavy current must have conductors of gauge sufficient to carry safely the maximum amount of current that is likely to pass through them. The leads should be of the proper length with just a little length spare for repairs etc. In one instance, a fire occurred in an exchange where, in replacing a faulty power lead, a whole coiled bundle of wire was used; the coil being kept over the rack caused excessive heating of the wire which resulted in fire. Even for temporary repairs, unnecessary long lengths of wire, or the wire of gauge smaller than what is needed, should not be used.
- In Switch rooms, the passages around the equipment racks should be kept clear of combustible materials like books, directories, files, bottles of oil, methylated and denatured spirit, old pieces of cable etc. as they are likely to assist in spreading fire.
- If blow lamps have to be used for plumbing etc. special precautions should be taken to prevent fires. Naked lights should not be used in the rooms.
- A fuse of proper rating shall be provided at the negative terminal of the battery sets.
- In all Electronic Exchanges an emergency switch shall be provided in switch-room, close to the entry to cut off power to the equipment, in case of an emergency.
Small Automatic Exchanges have been specially designed to function with the minimum of attention and even on unattended basis. In any unattended equipment of this type certain faults if not detected in time can result in a fire hazard. It is, therefore, imperative that the Officers responsible for the maintenance of exchange should inspect them periodically and pay particular attention to the following points.
- To ensure that no equipment is getting excessively hot.
- Check that fuses are of correct rating and that the fixing screws are tight.
- Check that the resistors are securely fixed and properly wired.
- Check the operation of fuses and release alarm.
- The result of such inspection should be recorded in the station log book.
- No bare wire shall be used in the fuses; only cartridge fuses shall be used.
- The power distribution shall be, as far as possible, by bus bars and they shall run in the free space which is open to easy inspection.
- The size of the bus bars should take into consideration, derating of the current carrying capacity on account of location, materials used, insulation provided etc.
- The bus bars shall always be run with the narrow side facing the ground i.e. the longer side shall be vertical.
- The positive and negative bus bars shall be colored with a suitable insulated coating / covering of red for positive and blue for negative. Negative bus bar is to be insulated by tapes & positive by insulating paint.
- The crossing of distribution cables over the bus bars shall be avoided.
- Crossing of light fittings and air-conditioning ducts above bus bars shall be avoided. If unavoidable, the ducts shall be covered by fire proof material and shall be properly anchored.
- In multi-exchange buildings, when a common power plant feeds more than one Exchange, independent bus bars shall be provided for each Exchange.
- Battery room shall be well ventilated. Battery shall stand directly on durable non-ignitable, non-absorbent, non-conductive material such as glass, porcelain or glazed earthen ware. The material shall rest on a bench which shall be kept dry and insulated from earth. All conductors connecting the supply terminals to batteries shall have either rubber or tough compound insulation without tape or braid. If glazed windows are provided in the battery room, the glass shall be painted to make it opaque to direct sunlight inside the room.
- Bare open wire type fuses should not be used. Fuses should be of porcelain box type or bolted cartridge type.
- National Building Code Part – IV – Fire Protection.
- IS 1641: Code of Practice for Fire Safety of Buildings – General Principle of Fire Grading and Classification.
- IS 1644: Code of Practice for Fire Safety of Buildings (General) – Exit Requirements and Personnel Hazards.
- IS 1646: Code of Practice for Fire Safety of Buildings – Electrical Installations.
- IS 2189: Code of Practice for Selection, Installation and Maintenance of Automatic Fire Detection and Alarm System.
- IS 2190: Code of Practice for Selection, Installation and Maintenance of First aid, Fire Extinguishers.
- IS 3844: Code of Practice for Installation and Maintenance of Internal Yard Hydrants and Hose Reels in Multi-storey Buildings.
- BS 6366: British code of practice for fire protection of electronic data processing installations.
- Regulations of Tariff Advisory Committee (insurance Association of India).
- French PTT Regulations on Fire Protection – Vol I & II.
- Report of Committee to investigate fire in Malabar Hill Telephone Exchange.
- IE Rules, 1956.
- Guidelines for prevention of fire in Telecom Buildings.